A standard 1:1 v/v pine bark and sand potting medium was characterized physically by particle size distribution, bulk density (BD), total pore space, porosity at 50 cm H2O tension and porosity at >50 cm H2O tension. A potting medium identical to the standard was constructed from component milled pine bark and sand particles. Phaseolus lunatus L. ‘Jackson Wonder’ plants grown in the 2 physically similar media, under a standard cultural program, were essentially identical. Construction of a potting medium from a prescribed screen analysis provides a means to quantify variation which exists within a medium assumed to be uniform.
Volume of loose media was determined accurately by a devised mechanical method and used for bulk density (BD) calculations. BD associated with increasing percentages of pine bark and/or sand potting media were plotted. Linear increase in BD associated with increasing percentage of sand in the medium was used to predict the percentage by volume of sand and/or bark in an unknown mixture of the two components. The technique should be useful in synthesis studies utilizing pine bark and sand as medium components.